076 
fxus62 kcae 070550 
afdcae 
area forecast discussion 
National Weather Service Columbia SC 
149 am EDT Tuesday Oct 7 2008 


Synopsis... 
high pressure over the East Coast will dominate through Tuesday. 
A developing frontal system in the Southern Plains will bring 
unsettled weather to the area later in the week. 


&& 


Near term /until 7 am Tuesday morning/... 
high pressure centered over southeast Canada continues to ridge 
down the East Coast. A weak cold front is currently draped across 
the Virginia/NC border. Expect mainly clear skies tonight. Overnight 
lows mainly in the 50s. 


&& 


Short term /7 am Tuesday morning through Wednesday night/... 
upper ridge over the East Coast begins to flatten Tuesday as 
deepening upper trough moves into the MS valley. Weak cold front 
over the middle Atlantic will drop into the northern SC midlands by 
early Tuesday morning before washing out later in the day. As a 
result...expect some weak cold air damming conditions across the 
northern counties for Tuesday so will trim afternoon highs there a 
few degrees. Surface winds will shift more easterly in response 
to an approaching low pressure system moving out of the middle 
Mississippi Valley. 


Low level moisture will be increasing on Wednesday with easterly 
surface onshore flow and 850 mb winds flowing off the Gulf of 
Mexico ahead of the low pressure system. Will carry low chance 
probability of precipitation for late Wednesday afternoon for the possibility of some 
isolated showers. 


&& 


Long term /Thursday through Monday/... 
uncertainty continues in the extended forecast as medium range 
models remain divergent with their solutions...leading to a low 
confidence forecast. GFS hints more at closing off an upper low 
over the Tennessee Valley by Wednesday night and moving it over 
the Carolinas on Thursday and into the middle Atlantic by Friday. 
The NAM/European model (ecmwf) is not quite as progressive in its solution as it 
develops the closed low over the lower MS valley later on 
Wednesday and slowly pushes it east over the Carolinas late 
Thursday and Friday. Mainly a dry forecast through the weekend 
into early next week. Overall stayed close to HPC solution. 


The one thing that is becoming more clear is that the Wednesday 
night and Thursday periods seem to be when the best chances for 
rain can be expected. Will continue with likely probability of precipitation Wednesday 
night along and south of a cae-ogb line and carry highs chance 
probability of precipitation on Thursday. Due to the uncertainty of the evolution of this 
system...will leave the remainder of the forecast as is...leaning 
toward persistence. 


&& 


Aviation /06z Tuesday through Saturday/... 
the fog potential appears less late tonight compared to last night. 
Expect an increase in boundary layer winds toward daybreak. 
The NAM and GFS show the pressure gradient becoming tighter during 
the early morning hours as the ridge builds into the area from 
the north. The sref guidance plus the met and mav MOS 
temperature-dew point temperature spreads support VFR conditions 
early this morning. Visibilities already around 6 miles at most taf sites. 
Could see visibilities lower to 2 or 3 miles before boundary layer winds 
increase. Should see patches of middle and high level cloud move 
through the area this morning. After 13z...the dry ridging should 
maintain VFR conditions through the day Tuesday. 


Extended outlook...widespread MVFR or IFR conditions may occur 
Wednesday night through Friday associated with low pressure moving 
into the area. 


&& 


Cae watches/warnings/advisories... 
SC...none. 
Georgia...none. 


&& 


$$ 


Aviation...10